In order to actively cope with the natural disasters, such as an earthquake and a tsunami, it is necessary to establish an earthquake and tsunami warning system, hereinafter referred to as ETWS. With this system, it is able to promptly transmit information related to the disasters to subscribers when a natural disaster such as an earthquake or a tsunami happens, so that the influences of such disasters on human can be reduced.
FIG. 1 shows a network architecture diagram of a public land mobile network (PLMN) operator providing earthquake and tsunami warning services to subscribers via the ETWS. When a disaster event is imminent or has taken place, the government or other organizations issue a warning notification to the PLMN operator which transmits warning notification messages to subscribers via the ETWS included in the frame of FIG. 1.
Depending on different urgency and purpose, the warning notification message may be classified into two types: the first type of notification message is called primary notification message containing the most important disaster information (for example, earthquake or tsunami being imminent), wherein the primary notification messages are to be transmitted to subscribers via the system within 4 s; and the second type of notification message is called secondary notification message containing auxiliary information related to the disasters (for example, where to get the assistance), wherein the secondary notification messages are to be transmitted to subscribers via the system within 10 s to 30 s. The primary notification message consists of two parts, i.e. basic information and security information, wherein the basic information contains contents of warning type, warning area and the like, and the basic information is 5 bytes long; and the security information is used for providing a digital signature and a time stamp to the basic information, and the security information is about 50 bytes long.
In a long term evolution (LTE) system, the ETWS framework suggested by the prior art is shown in FIG. 2. The ETWS is implemented by adopting a CBC (cell broadcast centre) core network, and the network framework and interfaces of the ETWS are shown in FIG. 2, including an evolved universal terrestrial radio access network (E-UTRAN), a mobility management entity (MME), a serving gateway (S-GW), a packet data network gateway (P-GW), a home subscriber server (HSS), a policy and charging rules function (PCRF) entity and other support nodes. Based on the network architecture, when a base station (also called evolved node B, i.e. eNB) in the E-UTRAN transmits an ETWS primary notification message to a terminal (also called user equipment, i.e. UE) via an air interface Uu, the time delay requirement being within 4 s for transmitting the primary notification message cannot be met if taking the manner of paging the UE first and then transmitting the ETWS primary notification message to the terminal in the next system message modification period in a system message (usually 5 s later).